Fuel cell system and scavenging method of fuel cell

Abstract

A fuel cell system has a battery, a gas supply portion, a temperature acquisition portion configured to acquire a presumed temperature that is presumed to reach during the operation stop of the fuel cell; and a scavenging controlling portion. When it is determined that the presumed temperature is a predetermined temperature or more at the time of the operation stop of the fuel cell, the scavenging controlling portion performs the stop-time scavenging operation with a first scavenging ability; and when it is determined that the presumed temperature is less than the predetermined temperature, the scavenging controlling portion performs the stop-time scavenging operation with a second scavenging ability higher than the first scavenging ability.

What is claimed is: 
     
       1. A fuel cell system comprising:
 a battery configured to supply electric power at least during an operation stop of a fuel cell; 
 a temperature sensor configured to detect the temperature of the battery; 
 a gas supply portion configured to receive the electric power supplied from the battery and supply gas to the fuel cell; 
 a temperature acquisition portion configured to acquire, from the temperature sensor, the temperature of the battery during the operation stop of the fuel cell; and 
 a scavenging controlling portion programmed to control the supply of the gas to the fuel cell from the gas supply portion at the time of the operation stop of the fuel cell, and perform a stop-time scavenging operation to scavenge the fuel cell, wherein the scavenging controlling portion is programmed to:
 when it is determined that the temperature of the battery is equal to or greater than a predetermined temperature at the time of the operation stop of the fuel cell, perform the stop-time scavenging operation with a first scavenging ability providing a first amount of gas supplied to the fuel cell throughout the stop-time scavenging operation; and 
 when it is determined that the temperature of the battery is less than the predetermined temperature at the time of the operation stop of the fuel cell, perform the stop-time scavenging operation with a second scavenging ability providing a second amount of gas supplied to the fuel cell throughout the stop-time scavenging operation, the second amount of gas being larger than the first amount of gas. 
 
 
     
     
       2. The fuel cell system according to  claim 1 , wherein the scavenging controlling portion is further programmed to:
 when the operation of the fuel cell is stopped, control the supply of the gas from the gas supply portion to the fuel cell at a predetermined timing during the operation stop of the fuel cell, and perform a parking scavenging operation of scavenging the fuel cell; 
 when it is determined that the temperature of the battery during the operation stop of the fuel cell is equal to or greater than the predetermined temperature, perform the parking scavenging operation; and 
 when it is determined that the temperature of the battery during the operation stop of the fuel cell is less than the predetermined temperature, not perform the parking scavenging operation. 
 
     
     
       3. The fuel cell system according to  claim 2 , wherein:
 when it is determined that the temperature of the battery during the operation stop of the fuel cell is not less than a threshold temperature higher than the predetermined temperature, the scavenging controlling portion is programmed not to perform the stop-time scavenging operation. 
 
     
     
       4. The fuel cell system according to  claim 2 , wherein:
 the scavenging controlling portion is programmed to determine whether or not a predetermined condition under which the fuel cell is frozen is satisfied; and 
 at the time of the operation stop of the fuel cell, when it is determined that the predetermined condition is not satisfied and the temperature of the battery is not less than a threshold temperature higher than the predetermined temperature, the scavenging controlling portion is programmed not to perform the stop-time scavenging operation. 
 
     
     
       5. The fuel cell system according to  claim 4 , wherein:
 the scavenging controlling portion is programmed to perform scavenging on an anode side of the fuel cell and scavenging on a cathode side of the fuel cell individually in the parking scavenging operation; and 
 the scavenging controlling portion is programmed to:
 i) when it is determined that the condition is not satisfied and it is determined that the temperature of the battery during the operation stop of the fuel cell is equal to or greater than the threshold temperature, perform the scavenging on the anode side of the fuel cell and the scavenging on the cathode side of the fuel cell in the parking scavenging operation; and 
 ii) when the condition is satisfied or it is determined that the temperature of the battery during the operation stop of the fuel cell is less than the threshold temperature and not less than the predetermined value, perform the scavenging on the anode side in the parking scavenging operation. 
 
 
     
     
       6. The fuel cell system according to  claim 1 , wherein the scavenging controlling portion is programmed to:
 supply a larger amount of gas per unit time to the fuel cell when performing the stop-time scavenging operation with the second scavenging ability than when performing the stop-time scavenging operation with the first scavenging ability; and 
 perform the stop-time scavenging operation with the second scavenging ability and the stop-time scavenging operation with the first scavenging ability for the same period of time. 
 
     
     
       7. The fuel cell system according to  claim 1 , wherein the scavenging controlling portion is programmed to:
 supply a same amount of gas per unit time to the fuel cell when performing the stop-time scavenging operation with the second scavenging ability and when performing the stop-time scavenging operation with the first scavenging ability; and 
 perform the stop-time scavenging operation with the second scavenging ability for a longer time than the stop-time scavenging operation with the first scavenging ability. 
 
     
     
       8. A scavenging method for a fuel cell, the method being for scavenging the fuel cell at the time of an operation stop of the fuel cell by supplying gas to the fuel cell by use of electric power from a battery, the method comprising:
 acquiring a presumed temperature that a temperature of the battery is presumed to reach during the operation stop of the fuel cell; and 
 determining whether or not the presumed temperature is a predetermined temperature or more, at the time of the operation stop of the fuel cell, wherein:
 i) when it is determined that the presumed temperature is the predetermined temperature or more at the time of the operation stop of the fuel cell, the scavenging of the fuel cell is performed with a first scavenging ability; and 
 ii) when it is determined that the presumed temperature is less than the predetermined temperature, the scavenging of the fuel cell is performed with a second scavenging ability higher than the first scavenging ability. 
 
 
     
     
       9. The method according to  claim 8 , wherein:
 when it is determined that the presumed temperature is the predetermined temperature or more, a parking scavenging operation is performed; 
 when it is determined that the presumed temperature is less than the predetermined temperature, the parking scavenging operation is not performed; and 
 the parking scavenging operation is performed such that, when the operation of the fuel cell is stopped, the supply of the gas to the fuel cell is controlled at a predetermined timing during the operation stop of the fuel cell, and perform the scavenging of the fuel cell. 
 
     
     
       10. The method according to  claim 9 , wherein:
 at the time of the operation stop of the fuel cell, when it is determined that the presumed temperature is not less than a threshold temperature higher than the predetermined temperature, the scavenging of the fuel cell performed with the first scavenging ability is not performed. 
 
     
     
       11. The method according to  claim 9 , wherein:
 it is determined whether or not a predetermined condition under which the fuel cell is frozen is satisfied; and 
 at the time of the operation stop of the fuel cell, when it is determined that the predetermined condition is not satisfied and the presumed temperature is not less than a threshold temperature higher than the predetermined temperature, the scavenging of the fuel cell performed with the first scavenging ability is not performed. 
 
     
     
       12. The method according to  claim 11 , wherein:
 in the parking scavenging operation, scavenging on an anode side of the fuel cell and scavenging on a cathode side of the fuel cell are performable individually;
 i) when it is determined that the condition is not satisfied and it is determined that the presumed temperature is the threshold temperature or more, the scavenging on the anode side of the fuel cell and the scavenging on the cathode side of the fuel cell are performed in the parking scavenging operation; and 
 ii) when the condition is satisfied or it is determined that the presumed temperature is less than the threshold temperature and not less than the predetermined value, the scavenging on the anode side is performed in the parking scavenging operation. 
 
 
     
     
       13. The method according to  claim 8 , wherein the temperature of the battery, detected at the time of the stop of the fuel cell, is acquired as the presumed temperature. 
     
     
       14. The fuel cell system according to  claim 1 , wherein the scavenging controlling portion is programmed to:
 perform the stop-time scavenging operation with the first scavenging ability providing a first anode scavenging amount of gas supplied to an anode of the fuel cell and a first cathode scavenging amount of gas supplied to a cathode of the fuel cell; and 
 perform the stop-time scavenging operation with the second scavenging ability providing a second anode scavenging amount of gas supplied to the anode and a second cathode scavenging amount of gas supplied to the cathode of the fuel cell, wherein the second anode scavenging amount of gas is greater than the first anode scavenging amount of gas and wherein the second cathode scavenging amount of gas is greater than the first cathode scavenging amount of gas.